[unreadable] [unreadable] Pancreatic ductal adenocarcinoma (PDAC) has one of the lowest incidence-adjusted survival rates of any form of cancer. Previously we demonstrated that tumor grade is the only consistent multivariate predictor of survival at our cancer center. Thus, the definition of factors regulating the transition from low-grade tumors to high- grade tumors should provide important insight into improved diagnostic avenues, including potential early detection screening and possibly targeted treatment, neither of which are currently available for PDAC. We have identified the hematopoietic tyrosine kinase syk as a marker of differentiation/tumor suppressor in PDAC. Syk is uniformly expressed in the cytoplasm and nucleus of normal pancreatic ductal epithelial cells, as well as low grade PanIN's. Syk expression is maintained in low grade PDAC cells (G1,G2), irrespective of invasive capability, however syk is absent from high grade PanIN's and PDAC (G3), and syk expression correlates positively with patient survival. Syk has been described as a tumor suppressor in breast cancer, with roles in overt cell signaling as well as indirect regulation of gene expression through HDAC binding and the Sp1 system. Our preliminary evidence demonstrates that in PDAC, syk is involved in [unreadable]-catenin signaling, a known regulator of the epithelial-mesenchymal transition. In support of this contention, stable ectopic expression of syk in syk-negative Panc-1 cells resulted in downregulation of the [unreadable]-catenin-regulated gene products Akt and CD171 (L1-CAM), which are both overexpressed by these cells. Reciprocally, suppression of syk expression in endogenously syk-positive BxPC3 PDAC cells and immortalized normal pancreatic ductal epithelial cells results in de novo CD171 expression. Moreover, Panc1 cells expressing syk are growth retarded in vitro and in vivo, and exhibit enhanced sensitivity to both radiation and gemcitabine, the chemotherapeutic agent of choice in PDAC. We hypothesize that syk is a central mediator of the malignant phenotype in PDAC. Therefore, in Aim 1 we will identify genes important for syk-regulated PDAC progression by global genomic profiling of endogenously syk-negative Panc1 cells into which we have re-introduced syk, and reciprocally, using endogenously syk-positive BxPC3 cells into which we have introduced a dominant-negative syk, both in vitro and in vivo. In Aim 2, candidates will initially be screened using a bank of cell lines and promising targets will be verified using clinical samples. Importantly, since syk expression is lost in late-stage PanIN's, which are the likely precursors of poorly-differentiated tumors, reintroduction of syk into G3 tumor cells may identify previously unknown mediators of early changes in PanIN development and progression. [unreadable] [unreadable] [unreadable]